Due to the rapid growth of wireless communications and ever increasing bandwidth demands from users, increasing spectrum resources are required. In the following, the term spectrum resources defines the radio frequency bandwidth in one or more frequency bands within the radio frequency spectrum which is available to be used for a defined radio standard.
Within the conventional spectrum framework, most of the spectrum bands are exclusively allocated to specific license holders for dedicated applications areas (e.g. broadcasting services or mobile communication services). Several license bands are underutilized however (for example, TV broadcasting, military bands), which results in spectrum wastage.
The standard IEEE 802.22 has been formed to develop the air interface specifications for secondary access to television channels where these channels have (local and/or temporal) “white spaces” in their utilization, and indeed spectrum sensing forms one of the key features of most envisaged “cognitive” radio systems. Noise uncertainty, multipath fading and shadowing are some of the fundamental properties of wireless channels which are responsible for limiting the performance of spectrum sensing.
Publications such as WO2011156114 (Microsoft) describe, for example, if a first white space channel is unavailable, due to the presence of the primary user, then a second white space channel should be determined and used. An additional example, WO2011100103 (Microsoft), describes sensing white space information using collaborative sensing principles, and the use of proxy devices between database server and receiving device. A further Microsoft publication, WO2011119917, describes how users of cellular mobile systems may be selected to receive incentives to use a different frequency band, outside of the allocated cellular spectrum, if a base station is overloaded.
The sharing of white space information in communication networks, and using this information to configure a communications device is addressed in KR20110108308 (Nokia) and EP2391160 by the same company describes a time variant collaborative sensing of white space, coordinated by a central node.
WO2012003566 (WILAN) describes using databases to store and recall white space information, whilst WO2012068138 (Qualcomm) describes location specific spectrum sensing.
In detail WO2011119917 (A2), CELLULAR SERVICE WITH IMPROVED SERVICE AVAILABILITY (Microsoft), describes a cellular communication system in which overload of a base station is averted by offering users the option to communicate using a spectrum outside of the spectrum allocated for cellular communication. Incentives are offered to connect to the base station using the alternative spectrum, which may not support communications at the same rate as could be supported using the spectrum allocated to the base station for cellular communications. Users may be selected to receive an offer to receive incentives based on range to the base station, with users closer to the base station being more likely to receive such an offer. The cellular communications system may be a 3G wireless system, and the alternative spectrum may be white space in the digital TV spectrum.
In summary, users selected to receive incentives to use a different frequency spectrum, outside of the allocated cellular spectrum, if the base station is overloaded.
WO2011156114 (A2), TRANSMITTING DATA IN A WIRELESS WHITE SPACE NETWORK, discloses a computer-implemented method for transmitting data over a wireless network using white spaces. A first white space transmission channel is determined for communicating with mobile client devices. Wireless communication takes place with the mobile client devices over the first white space transmission channel. If the first white space transmission channel becomes unavailable to one of the mobile client devices because of the presence of a primary user on the first white space transmission channel, a different white space transmission channel is determined for communicating with the mobile client device that is affected. Thereafter, communication with the affected wireless device takes place on the different white space transmission channel, while unaffected devices continue to communicate on the first white space transmission channel.
In summary, if a first white space channel is unavailable, due to the presence of the PU, then a second white space channel is determined and used.
WO2011100103 (A2)—DISTRIBUTED DATABASE ACCESS FOR SPECTRUM ACCESS (Microsoft) discloses a bootstrapping technique for wirelessly obtaining white space data that may be used to identify an available white space channel for connecting to a service. Portable wireless devices may collaborate to provide white space data to a device requesting such data. A requesting device transmits a request for the white space data using, for example, an unlicensed band. A device receiving the request may transmit a copy of the data to the requesting device. The transmitted copy may be obtained by the receiving device from a local data store or may be provided from a database server to which the receiving device is connected. In the later case the receiving device acts as a proxy between the database server and the requesting device. Once the white space data is received by the requesting device it may be used to select a channel for communication in the white space.
In summary, the collecting of white space information using collaborative sensing principles, also includes a proxy devices between database server and receiving device.
KR20110108308 (A), COLLABORATIVE SPECTRUM SENSING IN RADIO ENVIRONMENT (Nokia), discloses a system for configuring wireless communication in apparatuses based on sensed spectrum information. Apparatuses interacting via a shared information space may exchange configuration information that may, for example, comprise communication transport information. The configuration information may then be utilized in formulating spectrum sensing parameters that are distributed to one or more of the apparatuses via the shared information space. The spectrum sensing parameters may be used by the apparatuses for performing signals sensing operations in their respective environments, the results of which may be shared via the shared information space. The spectrum sensing results may then be utilized to configure and/or manage communications in one or more of the apparatuses.
In summary, the document describes the sharing of white space information in communication networks, and using this information to configure a communications device.
EP2391160 (A1), Method and apparatus to select collaborating users in spectrum sensing (Nokia) discloses that in a first time interval TI a first frequency band FB is pseudorandomly selected from a designated spectrum, and a first analysis result is determined by sensing the first FB during the first TI and then transmitted. In a second TI a second FB is pseudorandomly selected from the designated spectrum, and a second analysis result is determined by sensing the second FB during the second TI and then transmitted. Where multiple devices do this the entire spectrum is sensed, each band by a subset of devices that changes at each TI, and so any unused or underutilized spectrum is searched by the collaborative spectrum sensing, which avoids propagation problems such as fading. Also, a central node can assure various collaborating users report different FBs in different TIs such that the subset of reporting users changes for at least one of the bands in each subsequent reporting TI. Sensing and communication can be performed in different portions of the same network defined transmission time interval.
In summary, a time variant collaborative sensing of white space, coordinated by a central node is performed.
WO2012068138 (A1), GEO-LOCATION AIDED SENSING (Qualcomm), discloses a challenge to develop a technique of accurately and efficiently determining an available communication channel. In accordance with some embodiments disclosed herein, techniques for sensing a primary user of a particular communication channel are performed more efficiently. In some implementations, a geo-location of a communication device is combined with a sensing algorithm in order to more efficiently perform spectrum sensing. In some implementations, a geo-location and an accuracy determination may be used to determine all required sample regions in order to ensure that a primary user is not present in a particular location.
WO2012003566 (A1), TV WHITE SPACE DEVICES USING STRUCTURED DATABASES (WILAN), discloses a two-level database structure for use by unlicensed TVBD devices operating in TV white space comprises a central database and local databases. The central database comprises two sub-database: the central licensed database which maintains information about all licensed TV devices and the central unlicensed database which maintains information about unlicensed wireless devices operating in TV spectrum. The local database is created by each TVBD device or TVBD network when it initiates and it stores information related to all transmitters in the local area, including location, power transmission levels, operating schedule, sensing results, backup channel information. The local databases communicate with central database to query it about licensed usage of TV spectrum and register with central database. The local databases communicate with each other to exchange information about channel usage, sensing results, transmission patterns and other information that will allow the local databases to negotiate coexistence without central coordinator. The locally implemented negotiation prevents the overloading of the central database.
Most descriptions of “white space” related inventions refer to the primary transmitter as being a broadcast TV transmitter. An example is illustrated in FIG. 5: if TV transmitters are using one frequency for local television in one city (for example, M in FIG. 5), then it is not possible to use the same frequency for a different local television transmission in another moderately close city (for example, L), because receivers half-way between would receive two different transmissions on that same frequency. These would then interfere with each other. Accordingly, it is necessary to travel further away to a distant city (for example, B) before using that frequency for something else. As a result, it can be the case that frequencies reserved for television transmissions in one city are not actually used in the city itself. Accordingly it can then be re-used for white space transmissions, provided that the transmissions are at a low enough power that they do not interfere with television receivers in cities which use the frequency for broadcast television.
However, “white space” usage can be defined with a broader scope. It is conceivable that the primary could also be another telecommunication system. For example, nearby GSM base stations use different frequencies in the same way as the TV transmitters L and M (FIG. 5) (although this is not the case for 3G or 4G). Also, any telecommunication system has guard bands or frequency reuse factors >1, respectively.
The concept of access to different “spectrum layers” may include access to white space spectrum, but may also include access to spectrum owned by the network operator, free access to unlicensed spectrum etc. and which may be selected with different priorities according to user access right, QoS constraints etc.
The publications discussed above do not describe the use of route information, which describes time variant routes which may be taken periodically by users and their devices, and furthermore do not describe contextual application needs such as bandwidth and latency    (i) Whilst location information is used (as referred to in the publications discussed above), no account is made of a user's route. This is important, as a user's route will allow a prediction to be made of their future communication (and hence network resource) needs, and as a result (a) the likely availability of network spectrum resources and (b) the match of user needs to available network spectrum resources. A prediction of (a) and (b) is useful, as this can determine which policies are used in the transmission of data (for example, an increased buffer size may be established) if it is known that the user will enter an area with poor network and/or spectrum resource availability for a specific user priority class.    (ii) Different applications have different bandwidth, latency and robustness needs. To maximize the Quality of Experience (QoE), it is important that the application needs are matched as closely as possible to the available spectrum resources and network resources, anticipating future requirements if possible by both predicting future application needs and location based routes which are taken by the user.